1. Field of the Invention
The present invention relates to a configuration of a backlight which is arranged in a liquid crystal display. In particular, the invention relates to a backlight which is formed of a light-emitting diode and a configuration of a cooling device which is arranged for the backlight. In addition, the invention relates to a configuration of a display device including a backlight which is formed of a light-emitting diode and a configuration of a cooling device which is arranged for the backlight.
2. Description of the Related Art
A liquid crystal display is expected to have a larger screen, and be reduced in weight, thickness, and power consumption compared to a conventional cathode-ray tube (CRT). In recent years, a liquid crystal display has been used for various display devices such as TV and a monitor for a personal computer.
Since liquid crystal elements do not emit light by themselves, for example, a backlight which functions as a light source is arranged on a back surface portion of a liquid crystal panel. Conventionally, although a cold cathode fluorescent tube in which hydrargyrum or xenon is sealed in a fluorescent tube (Cold Cathode Fluorescent Lamp: CCFL) is employed as the backlight, there is a problem in that a color reproduction area is small.
Therefore, in recent years, a technique where three colors of light-emitting diodes (Light Emitting Diode: hereinafter described as LED in this specification), which are red, green, and blue are employed as backlight as a substitute for a cold cathode fluorescent tube has been attracted attention. By employing an LED to a backlight, a color reproduction area is remarkably wider than a conventional cold cathode fluorescent tube and further a color which is difficult to realize in a display utilizing a fluorescent material such as CRT or plasma display can be expressed. In addition, since a driver circuit of the backlight can be simplified compared to a conventional display device, cost can be reduced.
Meanwhile, when a liquid crystal display having a backlight is consecutively used, the large amount of heat is released. Since characteristics of liquid crystal elements or elements such as a transistor which drives the display device change by this heat from the backlight, this becomes a possible cause for a display defect such as color unevenness or a malfunction. In addition, the heat from the backlight becomes a possible cause for deformation of the display device. More particularly, in the case of employing an LED to the backlight, display unevenness or color unevenness is generated since characteristics of LED itself change by heat from the LED.
Thus, in order to radiate the heat from the backlight, various means for radiation of heat are provided. For example, as a conventional technique, an air-cooled cooling device where the heat is radiated by sending cooling air to the backlight with a cooling fan is employed (see Reference 1: Japanese Published Patent Application No. 10-96898).
However, in an air-cooled cooling device, since oscillation is generated by an operation of a cooling fan and noise is generated by hissing sound of a cooling fan, it requires new countermeasures for oscillation and noise. In addition, since the amount of heat generation increases as a liquid crystal panel is enlarged, there is concern in that the heat cannot be cooled enough only by an air-cooled cooling device.